KR20110029338A - Bearing for spindle motor and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A bearing for a spindle motor and a method of manufacturing the same are provided to prevent the decrease of the inner diameter of a bearing and to enhance the dimension precision of the inner diameter, since the contraction of the inner diameter becomes smaller as the outer diameter contracts. CONSTITUTION: A method of manufacturing a bearing for a spindle motor is as follows. Metallic powder is mixed with addition. The mixed powder is filled in a mold, the density of the metallic powder gets higher in its inner part and gets lower in its outer part. The metallic powder with different densities is pressed to make an intermediate green compact of a product shape. The intermediate green compact is heated to a temperature below a melting point to make a sintered body, which has a physical property necessary for a product.

Description

BEARING FOR SPINDLE MOTOR AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a bearing for a spindle motor for rotatably supporting a rotating shaft and a method of manufacturing the same.

The spindle motor is a kind of BLDC motor driven by the rectification of the semiconductor device, and has a high precision rotation characteristic. Such a spindle motor is widely used as a rotating means of a recording medium that requires a high speed rotation such as a hard disk drive or an optical disk drive.

In general, the spindle motor has a structure in which a stator is installed on a base plate to which a circuit board is coupled, and a rotor is rotatably coupled to the stator. The circuit board may be provided with an encoder for detecting the rotational speed of the rotor.

The stator includes a core coupled to a bearing housing coupled to the base plate and a coil wound around the core, and the rotor includes a rotor yoke and a magnet coupled inside the rotor yoke. The rotor yoke may rotate together with the rotation shaft by being coupled to a rotation shaft rotatably coupled to the stator.

In the spindle motor of this structure, when a current is applied to the coil, the core is magnetized to push the magnet. The electromagnetic action of these cores and magnets allows the rotor and rotating shaft to rotate at high speeds of thousands or tens of thousands of rpm.

A rotating shaft rotatably supporting the rotor is rotatably coupled to a bearing installed inside the bearing housing. An oilless bearing is used as a bearing for a spindle motor. Oilless bearings are a type of sliding bearings that have a number of pores and are impregnated with oil, so there is no need to supply oil separately during use.

However, the conventional spindle motor bearings are easily contracted in the radial direction when they are press-fitted into the bearing housing to reduce the inner diameter. Therefore, it is difficult to design the inner diameter which can stably support the rotating shaft.

In addition, conventional bearings for spindle motors have a strong pressing force upon press-fitting into a bearing housing, and the inner diameter of the bearing is severely reduced so that much of the inner circumferential surface thereof is cut (Sizing), thereby increasing manufacturing time and manufacturing cost. And if the inner peripheral surface is cut a lot to enlarge the inner diameter, fine debris from the bearing is likely to remain inside the bearing. In this case, there is a problem that the service life is shortened by increasing friction with the rotating shaft.

The present invention has been made to solve the above problems, and to provide a bearing for a spindle motor and a method of manufacturing the same that can suppress the reduction of the inner diameter when pressed in the bearing housing by making the outer diameter of the bearing lower than the inner diameter.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

In one embodiment, the bearing for a spindle motor of the present invention includes an inner diameter portion having an insertion hole in the center and an outer diameter portion having a different density of internal structure than the inner diameter portion.

Here, the outer diameter portion has a lower density of the internal tissue than the inner diameter portion may be disposed around the inner diameter portion.

In one embodiment, the manufacturing method of the bearing for the spindle motor of the present invention, the mixing step of mixing the metal powder and additives together, filling the mixed powder in the mold and increase the density of the metal powder inward and the metal outward Density control step of lowering the density of the powder, compression step to press the metal powder is adjusted to the density of the inner and outer sides to make an intermediate molded article shape, the physical properties required for the product by heating the intermediate molded article to a temperature below the melting point A sintering step of making the sintered body is provided, and an impregnation step of impregnating oil in the sintered body in a vacuum.

In the bearing for the spindle motor according to the embodiment of the present invention, when the inner diameter of the bearing having a relatively low density is first contracted when the bearing for the spindle motor is pressed, the shrinkage of the inner diameter is reduced. Therefore, the reduction of the bearing inner diameter can be suppressed, and the dimensional accuracy of the bearing inner diameter can be improved.

In addition, since the bearing for the spindle motor according to the embodiment of the present invention can reduce the amount of reduction in the inner diameter when the bearing is pressed into the bearing housing, it is not necessary to cut the inner peripheral surface of the bearing as much as in the prior art in order to fit the inner diameter. Therefore, manufacturing cost and manufacturing time can be reduced, and the risk that the fragments cut off from the bearing remain inside the bearing can be reduced.

In addition, the bearing for the spindle motor according to the embodiment of the present invention is impregnated with more oil in the pores of the outer diameter portion of the low density, it is possible to smoothly supply the oil to the rotating shaft. Therefore, wear between the bearing and the rotating shaft can be reduced, thereby extending the life of the product.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this process, the size or shape of the components shown in the drawings may be exaggerated for clarity and convenience of description. In addition, terms that are specifically defined in consideration of the configuration and operation of the present invention may vary depending on the intention or custom of the user or operator. Definitions of these terms should be made based on the contents throughout the specification.

1 is a schematic cross-sectional view of a spindle motor to which a bearing according to an embodiment of the present invention is applied. 2 is a cross-sectional view showing a bearing according to an embodiment of the present invention. 3 is an assembly view of a bearing and a bearing housing according to an embodiment of the present invention.

As shown in FIG. 1, the spindle motor 100 includes a base plate 110, a stator 120, a rotor 130, a rotation shaft 140, a bearing housing 150, and a bearing 160. The circuit board 115 is coupled to the upper surface of the base plate 110, and the bearing housing 150 is coupled through the base plate 110 in the middle of the base plate 110. The stator 120 is fixed to the bearing housing 150, and the rotor 130 is coupled to the rotation shaft 140. The rotating shaft 140 is rotatably supported by the bearing 160 coupled to the inside of the bearing housing 150.

The stator 120 includes a core 121 fixed to the bearing housing 150 and a coil 122 wound around the core 121. The rotor 130 includes a rotor yoke 131 coupled to the rotation shaft 140 and a mark net 132 disposed around an inner circumference of the rotor yoke 131. A clamping device 170 is installed on the rotor yoke 131 to prevent separation of the optical disk mounted on the rotor yoke 131. When a current is applied to the coil 122, the rotor 130 rotates together with the rotation shaft 140 by an electromagnetic force generated between the stator 120 and the magnet 132.

The core 121 has a through hole 123 formed in the center thereof, and the bearing housing 150 is inserted into the through hole 123 to fix the core 121 to the bearing housing 150. A bearing accommodation groove 151 is provided in the bearing housing 150, and the bearing 160 is press-fitted into the bearing accommodation groove 151.

2 and 3, an insertion hole 161 through which the rotating shaft 140 may be inserted is provided at the center of the bearing 160. Bearing 160 is a type of oilless bearing (Oiless bearing) that does not require the supply of oil during use. The bearing 160 is manufactured through a metal powder metallurgy method, and a plurality of pores capable of impregnating oil therein are provided therein. These oil impregnated sintered bearings are manufactured through processes such as mixing, compression, sintering and impregnation.

The bearing 160 according to an embodiment of the present invention partially changes the density of the internal structure of the bearing 160 in the process of compressing and sintering the metal powder. That is, the bearing 160 has a higher inner density than the outer portion, and the inner diameter portion 162 having the insertion hole 161 at the center and the outer diameter portion 163 having a lower density than the inner diameter portion 162. It can be divided into.

The difference in density of the internal structure of the bearing 160 is due to the difference in density of the metal powder to be sintered. After the metal powder is mixed, the density of the internal structure of the bearing 160 may be partially changed by sintering while increasing the density of the metal powder toward the inner circumferential surface and lowering the density of the metal powder toward the outer circumferential surface.

In the bearing 160 according to the embodiment of the present invention, when the compressive force is applied in the radial direction, the outer diameter portion 163 having a relatively low density of the internal tissue is first contracted. In addition, the outer diameter portion 163 has a low density, the pore size of the inside of the large oil can be impregnated.

Next, the manufacturing method of the bearing for spindle motors is demonstrated.

The bearing 160 is manufactured by metal powder metallurgy, and undergoes a mixing step, a density control step, a compression step, a sintering step, a shaping step, and an impregnation step.

First, the mixing step is a process of mixing the metal powder and the additive together. Various metals may be used as the metal powder.

Next, the density control step is a process of filling the powder mixed in the mold and applying an electromagnetic field to the powder to increase the density of the metal powder on the inside and to reduce the density of the metal powder on the outside. Various embodiments are possible, but, for example, by using a property of attracting the metal powder to a magnetic field, a magnetic field is strongly applied to a portion to increase the density of the metal powder and a relatively low magnetic field to a portion to decrease the density. Walk.

The compression step is a process of pressurizing a metal powder having a difference in density between the inside and the outside to form an intermediate molded product shape.

The sintering step is a process in which the intermediate molded body is heated to a temperature below the melting point to impart necessary physical properties to the product. The sintered body made through the sintering step is provided with pores therein.

By sintering, a solid powder is placed in a mold, pressed appropriately to harden, and then heated together to a temperature close to the melting point of the material, whereby the solid powder is bonded or deposited partly by contact at the contact surface of the solid powder. It is a process. It is suitable for forming composites (eg metals and ceramics) of materials that have a high melting point and are difficult to melt, or that do not mix when melted.

The shaping step is a process of raising the precision of the sintered compact by pressing the sintered compact into a precise mold.

Finally, the impregnation step is a process of impregnating oil into the sintered body in vacuum. At this time, the oil is impregnated into the pores inside the sintered body.

The bearing 160 manufactured through this manufacturing process has an inner diameter portion 162 having a high density of internal tissues and an outer diameter portion 163 having a relatively low density of the internal tissues. And since the oil is impregnated inside the bearing 160, there is no need to supply oil separately in use.

When the bearing 160 is pressed into the bearing housing 150, the bearing 160 is compressed in the radial direction and contracted in the radial direction. At this time, the shrinkage of the outer diameter portion 163 having a relatively low density is large and the shrinkage amount of the inner diameter portion 162 is small. Accordingly, the amount of reduction of the inner diameter of the bearing 160 is reduced compared to the related art, and the dimensional accuracy of the inner diameter of the bearing 160 is improved.

In addition, more oil is impregnated in the pores of the outer diameter portion 163 having a lower density, so that oil supply to the rotation shaft 140 may be smoothly performed for a long time. Therefore, wear between the bearing 160 and the rotating shaft 140 can be reduced, thereby extending the life of the product.

Although embodiments according to the present invention have been described above, these are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments of the present invention are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the following claims.

1 is a schematic cross-sectional view of a spindle motor to which a bearing according to an embodiment of the present invention is applied.

2 is a cross-sectional view showing a bearing according to an embodiment of the present invention.

3 is an assembly view of a bearing and a bearing housing according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100 ... spindle motor 110 ... base plate

115 Circuit Board 120 Stator

121 Core 122 Coil

130 ... rotor 131 ... rotor yoke

132 ... Magnet 140 ... Rotating shaft

150 ... Bearing housing 151 ... Bearing groove

160 Bearing ... 161 Insertion Holes

162 Inner diameter 163 Outer diameter

Claims (7)

A bearing for a spindle motor having an insertion hole into which a rotating shaft is inserted, An inner diameter portion provided at the center of the insertion hole and an outer diameter portion disposed around the inner diameter portion, A bearing for a spindle motor having a different density of the inner diameter portion and the outer diameter portion. The method of claim 1, The outer diameter portion has a lower density than the inner diameter bearing for the spindle motor. The method of claim 2, And the inner diameter portion and the outer diameter portion are integrally formed by sintering and molding metal powder. The method of claim 2, The inner diameter portion and the outer diameter portion of the spindle motor bearing is provided with a plurality of pores that can be impregnated with oil. A mixing step of mixing the metal powder and the additive together; Filling the mixed powder into a mold and increasing the density of the metal powder on the inside and lowering the density of the metal powder on the outside; A compression step of pressurizing the metal powder having different densities inward and outward to form an intermediate molded article shape; A sintering step of heating the intermediate molded body to a temperature below the melting point to produce a sintered body to which properties required for the product are imparted; And Impregnating the oil in the sintered body in a vacuum; manufacturing method for a spindle motor bearing comprising a. The method of claim 5, The density control step of manufacturing a bearing for a spindle motor comprising the step of applying electromagnetic to the metal powder filled in the mold in order to increase the density of the metal powder inward and to reduce the density of the metal powder outward. The method of claim 5, After the sintering step, inserting the sintered body into a mold and pressurizing to increase the precision of the sintered body manufacturing method of a bearing for a spindle motor.

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